Exhaust gases emitted from combined heat and power plants, coal power plants and/or incineration plants generally contain hazardous substances including hydrogen chloride, sulfur oxides, nitrogen oxides, dioxin and dioxin-like compounds. In this context, SCR accounts for a widespread method applied to eliminate, inter alia, specifically nitrogen oxides using NH3 as reducing agent.
As a small quantity of V2O5 and WO3 with TiO2 compose the catalyst system for the SCR denitrification process hereinbefore provided, the catalyst is to be contaminated with the impurities and contaminants contained in the exhaust gases in the course of operating time, which decrease its activity coming down to substantial termination of it after, on average, two to three years.
It has thus been required that a new remanufacturing method for deactivated, denitrified SCR catalysts be developed for its recovery and reclamation to its initial performance. This is therefore an urgent technology taking into consideration not only its future import substitution but also in the point of view of resource recycling.
The remanufacturing method mentioned above is classified into physical modes and chemical ones. One of the conventional, the physical technique includes procedures in which the deactivated catalyst is unloaded from the reactor and transported to the catalyst remanufacturing facilities in order to blow away the deposits on the surface of the catalyst by using compressed air. The carbon-based absorbate on the surface are combusted via a high-temperature roasting process. Another method includes ultrasonic cleaning of deactivated catalyst while it is submerged in distilled water.
On the other hand, cleaning by a diluted acid or alkali solution, or their mixed solution entailing ultrasonic cleaning has been attempted as a chemical method. Also, other alternative remanufacturing schemes which combine physical and chemical ones aforementioned are also known.
However, since the methods so far introduced requires the aged catalyst to be unloaded from the SCR reactor and transported to the catalyst remanufacturing facilities, damage to the catalyst during the transportation as well as cost increase are inevitable. In addition, there are problems such as the remanufacturing method such as physical grinding being disarranged and the aged catalyst being broken down or destructed during the remanufacturing
To this, KR 10-2012-0081914A created a catalyst recycling system including a multi-functional washing bath to cleanse the aged catalyst, but it protracts the cleaning period and because it carries out several subordinate treatments, the cleaning process is complicated. The so increasing operating costs are another problem.
Thus, the inventors hereby have committed to work through the challenges in that it is impossible to utilize ultrasonic devices for cleaning with the aged catalyst being set in the reactor in situ. Thus, they rounded out this invention having verified that optimal conditions for a remanufacturing solution and cleaning methods are to be employed to maximize the remanufacturing efficiency by exploiting the minimum remanufacturing solution within the shortest time possible. This prevents catalyst destruction, cuts down transportation costs as well as the enormous costs depending upon unloading and loading of the catalyst and shorten the remanufacturing time.